Re: [PATCH 4/8] jump label: Make arch_jump_label_text_poke_early()optional

[David Daney]

On 10/29/2010 01:37 PM, David Miller wrote:
> From: Steven Rostedt<rostedt@xxxxxxxxxxx>
> Date: Thu, 28 Oct 2010 09:55:52 -0400
>
> > From: David Daney<ddaney@xxxxxxxxxxxxxxxxxx>
> >
> > For the forthcoming MIPS jump label support,
> > arch_jump_label_text_poke_early() is unneeded as the MIPS NOP
> > instruction is already optimal.
> >
> > Supply a default implementation that does nothing.  Flag x86 and SPARC
> > as having arch_jump_label_text_poke_early().
> >
> > Cc: Jason Baron<jbaron@xxxxxxxxxx>
> > Cc: David Miller<davem@xxxxxxxxxxxxx>
> > Signed-off-by: David Daney<ddaney@xxxxxxxxxxxxxxxxxx>
> > LKML-Reference:<1286218615-24011-2-git-send-email-ddaney@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Steven Rostedt<rostedt@xxxxxxxxxxx>
>
> On the SPARC side, it's not that the nop isn't optimal, on sparc it's
> always 0x01000000.

That's what I thought.  You could remove your
arch_jump_label_text_poke_early() function to no determent.

> The issue is that when written an I-cache flush is
> necessary using a 'flushi' instruction.
>
> Does MIPS not need a flush when poking instructions?

Yes, it does.

> I find this hard to believe, although it's been some time since I
> last touched that architecture :-)

I just looked at my patch again.  I am indeed flushing the I cache
after patching the code, so I don't really know what you are talking
about.

David Daney
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